Electrical apparatus



May 21, 1929. c. G. SMITH ELECTRICAL APPARATUS Filed July 30, 1923 Patented May 21, 1929.

UNITED STATES PATENT OFFICE.

CHARLES G. SMITH, OF MEDFORD, MASSACHUSETTS, ASSIGNOB, BY MESNE ASSIGN- MEN'TS, TO RAYTHEON INC, OF CAMBRIDGE, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

ELECTRICAL Application filed July 30,

The present invention relates to electrical apparatus and more particularly to the type of electrical apparatus disclosed in the patents to Smith No. 1,545,207 July 7, 1925, and 1,617,171 February 8, 1927.

The basic invention disclosed in the first of the above mentioned applications consists of a novel type of insulating device having electrodes immersed in a gas and spaced apart a distance which is so short that gaseous ionization is normally impossible even under the influence of high electrical potentials. Such a device is insulating because electrons traversing the gaseous medium. under the action of an electric field are not allowed to collide with a suflicient number of molecules to initiate cumulative ionization and consequent conduction. However, as is disclosed in the second of the above men-, tioned applications, it has been found that such apparatus may be made conducting by causing electrons to take long paths through the gaseous region included between the electrodes. The specific form of the apparatus illustrated and described in the above application employs a magnetic field for defleeting the electrons in a direction transverse to their normal direction in such a manner as to lengthen their paths in the gas, thereby allowin more frequent collisions with gas molecul es.

The principal object of the present invention is to provide improvements in apparatus of this general nature whereby the gaseous. conduction may be controlled.

With this object in view, I have discovered in connection with such conducting devices that the intensity of electrical conduction depends materially upon the continuity of the ionization throughout the entire gaseous region and that if the means employed for lengthening the electron paths is partially or wholly suppressed over a small portion of the region, the conducting properties of the apparatus as a whole may be greatly altered. Accordingly, the present invention contemplates the provision of means for deflecting electrons and lengthening their paths in a gaseous region which is ofsufiiciently restricted dimensions to normally prevent ionization, together with means for altering the path lengthening means over a small portion of the region.

It has been found in connection with aparram'ros.

1923. Serial No. 654,644.

paratus of this type that if the ionization is distorted or suppressed over a sufiiciently large portion of the gaseous region, theconducting properties of the apparatus as a whole may be practically reduced to zero. However, the principal advantages of this invention reside in the fact that the conductivity of the gas may be caused to vary in step with any variations in the value of the path lengthening means, thus allowing the apparatus to be conveniently used for amplifying, generating or otherwise operating upon electrical oscillations.

The operation of this device may be briefly explained as follows: Conduction between electrodes in a gas subjected to a potential difference is believed to be caused by the collisions of electrons against gas molecules to ionize the molecules. The collision of an electron having sulficiently high velocity against a gas molecule tends to form from the molecule a positive ion and another electron. The electrons and ions so formed, together with the original electrons are in themselves free to collide with other molecules and ions. The conducting condition of a gaseous conducting device depends upon the cumulative effect of the ionization caused by a number of such collisions. In the present invention, an electron originally impelled directly between the electrodes is deflected by the path lengthening means so that its first collision with a gas molecule takes place at a considerable distance from the original po', sition of the electron. The ions and electrons so formed are in themselves able to introduce more ions and electrons intov the gas either by bombardment of the electrodes or by collision with other gas molecules. The elec-- trons are in turn deflected by the path lengthening means and cause further collisions at points removed from the first collision. It will thus be seen that the action is progressive and that if conditions are uniform over the entire electrode surfaces, the necessary conditions for cumulative ionization will be fulfilled and conduction will take place. However, if one or more of the collisions occur in a region where the path lengthening means is considerably suppressed, the electrons so formed will be impelled directly between the electrodes and will be unable to ionize other gas molecules. The cumulative ionizing action is thus forestalled and if the distortion is caused to take place over a sufiiciently large area, aseous conduction in the entire region may be suppressed. Further more, if the path lengthening means be allowed to fluctuate about a certain average.

value, the conductivity of the gaseous medium will be caused to vary in step with the fluctuations in the path lengthening means, thus allowing the apparatus to be used as a device for operating upon electrical oscillations.

In the drawings illustrating the preferred form of the invention, Figure 1 is an elevation in section of an apparatus embodying the features of the present invention; Fig. 2 is a section on line 2-2 of F ig. 1; and Fig. 3 is a diagram of a simple amplifying circuit embodying one of the devices shown in Fig. 1.

The illustrated embodiment of the invention employs a pair of electrodes preferably having plane opposing surfaces mounted within an insulating receptacle. The distance between the electrodes is short and comparable to the mean free path of electrons in the gas, that is so short that electrons I traveling directly across the gas space hefield impressed in the gaseous region by suitable magnetic poles. An auxiliary pole is provided for the purpose of distorting the magnetic field over a small portion of the gaseous region. The magnetization of the auxiliary pole may be caused to vary by any suitable means, thereby varying the conductivity of the entire gaseous medium included between the main electrodes.

As shown in Figs. 1 and 2, the glass receptacle 10 is provided with a reentrant stem 16 upon which are supported two annular electrodes 11 and 12 having plane surfaces spaced a distance apart which is short and comparable to the mean free path of electrons in the gas. The electrode 11 is supported upon stem 16 by means of metallic straps 15 and electrode 12 is conveniently supported upon a restriction 17 of the stem.

Both electrodes are so spaced within the receptacle that all points are sufiiciently close to the walls of the receptacle and stem so that ionization adjacent the insulating parts of the apparatus is normally impossible.

Suitable lead wires 11 and 12' are sealed into the receptacle and are attached to electrodes 11 and 12, respectively. For the purpose of lengthening the electron paths, two magnetic poles 4 and 5 are provided. The pole at is adapted to fit concentrically in the reentrant stem and pole 5 is annular in form and surrounds the receptacle 10. Poles 4 and 5 are magnetically energized by means of a permanent magnet 6. Pole 5 is not in the form of a complete ring but has a portion broken .apparatus of this type, the pole 8 may be conveniently made so as to subtend an'angle of approximately 22 degrees, that is, onesixteenth of the circumference.

The operation of this apparatus has been previously explained. From this explanation, it will be seen that if the auxiliary pole 8 is maintained at a zero value of magnetization, the ionization will be distorted in such amanner that the conductivity of the gaseous region as a whole will be greatly reduced and may, under certain conditions,'be made practically zero. It has been found that for certain values of magnetization of pole 8 between zero and that of pole 5, the conductivity of the gaseous region is extremely sensitive to variations in magnetization of pole 8. An amplifying system embodying one of these devices is shown diagrammatically in Fig. 3. This circuit comprises an input circuit 28 upon which the oscillations to be amplified are impressed and an output circuit 29 containing a source of direct current energy. The received oscillations which are impressed at 20 are transmittedto the in ut circuit 28 through a transformer 25. T e input circuit 28 includes the coil 18 upon the pole 8. A condenser 27 is included in the circuit for the purpose of tuning the circuit to the frequency of the oscillations. The output circuit 29 includes electrodes 11 and 12, together with a source of direct current energ 22.- The main magnetic means for lengthening the electron paths is indicated generally at 6. As previously stated, it is usually desirable to have the auxiliary magnetic pole operating about some average value of magnetization between zero and that of pole 5. To this end, the input circuit 28 preferably includes a source of direct current energy 23. For the utilization of the amplified oscillations, the output circuit 29 may be conveniently connected to a third circuit 35 by. means of a transformer 80. The amplifying action takes place through the distortion of the cumulative ionization and conduction of the gaseous region between the electrodes because of the variations in magnetization of the auxiliary pole 8 caused by the incoming oscillations.

While'it is preferred to employ the specific construction and arrangement of parts shown and described, it will be understood that this construction and arrangement is not essential except so far as specified in the claims and may be changed or modified Without departing from the broader features of the invention. v

The invention having been described, What is claimed is:

1. An electrical apparatus comprising two electrodes immersed in a gas, the distance between the electrodes being comparable to the mean free path of electrons in the gas, means for lengthening the electron paths in a direction parallel to the electrode surfaces, and means for altering the efl'ect of the path lengthening means over a restricted portion of the gaseous region between the electrodes.

2. An electrical apparatus comprising a gaseous regionand having one dimension so small that gaseous ionization under the action of an electric field coincident in direction With the small dimension is impossible, means for deflecting electrons and lengthening their paths in the gas, and means for distorting the effect of the path lengthening means over a restricted portion of said gaseous region.

3. An apparatus for operating upon-electrical oscillations comprising electrodes adapted to be oppositely charged immersed in a gas and spaced apart a distance comparable to the value of the mean free path of electrons in the gas, a pair of cooperating magnetic poles for the purpose of impressing a magnetic field in the region between the electrodes, an auxiliary magnetic pole adapted to be Varied by oscillations to Vary the magnetization of the auxiliary pole to alter the magnetic field over a portion of the gaseous region and vary the conductivity of the region as a Whole in accordance with the received oscillations.

\ 4. An apparatus for operating upon electrical oscillations comprising a gas filled receptacle, a pair of electrodes spaced therein a distance comparable to the value of the mean free path of electrons in the gas, and adapted to be excited by an electrical potential diflerence, a pair of cooperating magnetic poles adapted to impress upon the gaseous region a magnetic field parallel to the electrode, surfaces, an auxiliary magnetic pole for the purpose of distorting the magnetic field overa portion of the gaseous region between the electrodes, and a coil wound upon the auxiliary pole and adapted to be excited by the oscillations in a manner to vary the conductivity of the gaseous region in accordance therewith.

CHARLES G. SMITH. 

